Intestinal absorption of fat-soluble vitamins will be studied and characterized both in-vitro and in-vivo in experimental animals. Some studies will be conducted in normal human volunteers as well as in patients with disorders of the small bowel, liver, and pancreas. Primary emphasis will be placed on elucidation of the basic mechanisms of absorption of these compounds. The possible influences of intraluminal factors such as pH, bile salt concentrations, etc., will also be studied as to their effects of absorption of the fat-soluble vitamins. The absorption of related lipid-soluble compounds such as cholesterol, beta-carotene, and some fatty acids will also be studied.